1995 Sl320 a plethora of DTC's.Mystery.......H.E. E.L.P.

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Peter W Peternouschek - 14 Feb 2006 05:49 GMT

I don't quite know what to think about this problem.
Yesterday the MIL came on . The car seemed to drive allright and I did not
notice any degradation in performance.
I did a generic OBDII diagnostic with a laptop interface program/connector
at the OBDII connector and there were no trouble codes stored but the MIL
showed up as illuminated.
I cleared the non existent trouble codes, the MIL went out and I was happy
thinking I was home free.
I started the engine several times and the light stayed off.
This morning the MIL was back on again. This time I got out my Trisco scan
tool and retrieved these MB trouble codes via the 38 pin connector

007 Intake air sensor open circuit
015 Throttle valve pot actual value too low
022 EFP actuator signal in limp home mode
025 02 Sensor signal before Catalytic Converter incorrect
029 O2 Sensor Heater before Cataluytic converter too small current
030 O2 Sensor Heater before Catalytic Converter current too large
033 O2 Sensor Heater after Catalytic Converter current too large
039 Inj Valve cyl 2 shorted to positive
045 Inj Valve cyl 5 shorted to positive
047 Inj Valve cyl 6 shorted to positive
054 Mixture too lean at upper part load, Vacuum leak inj pressure
regulator/wear engine
061 Ignition sys output stage 3 cyl 1 misfire

I checked for codes at the OBDII connector with my lapttop/scantool
interface and there were no DTC's to retrieve.but the MIL was on. The O2
sensor test showed that the system was functioning OK and in closed loop.
Again I cleared the non existen DTC's
and the MIL went off.

Does anyone have a clue regarding what seems to be going on here .
Is the ECU on the way out ? I find it hard to believe that the car can have
all these problems and still run all right.

The car now has 93k miles. The wire harness apears OK. probably has already
been replaced. Anything else to look for?

Thanks
Peter

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Karl - 14 Feb 2006 14:32 GMT

You are trying to read OBD II codes on a OBD I car!!!!!
It does not work that way......
You need the old school MB HHT to read those faults.

Another thing that people don't realize is that generic scan tools for OBD II only read the P0xxx
codes. MB's also have P1xxx and P2xxx codes that go deeper to explaining the fault. By law, the
generic tools have to read the P0xxx faults, which they do.

> I don't quite know what to think about this problem.
> Yesterday the MIL came on . The car seemed to drive allright and I did not
[quoted text clipped - 37 lines]
> Thanks
> Peter

Reply to this Message

Peter W Peternouschek - 14 Feb 2006 16:01 GMT

My 1995 SL320 is an OBDII car. The Electronics for this car are a mix of
digital and analog. The generic OBDII interface adapter and program for my
laptop computer that I use worked fine for me once before and displayed the
correct PXXXX code when I had a problem with an O2 sensor sometime back. On
this go around however no PXXXX codes came up at all.

The TRISCO scan tool that I used to get the codes from the 38 pin connector
is MB specific
and displayed all the codes shown in my initial post. It is my understanding
the the Trisco scan tool is similar to the MB HHT.

> You are trying to read OBD II codes on a OBD I car!!!!!
> It does not work that way......
[quoted text clipped - 45 lines]
> > Thanks
> > Peter

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Tiger - 15 Feb 2006 16:23 GMT

The Trisco tool is the right tool for your car. Karl was just saying on the
OBDII part. As for your problem... is it possible you got a main wiring
harness problem? That is just too many DTC at one time.

ECU is always the last culprit... Computer on cars are super reliable that
they are rarely at fault, except for the newest cars on the market... that's
a different ballgame because there are too many computers.

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